Stuff and B****Y nonsense. Cease robbing toilet-seat bumpers and kiddie-nursery play-pen stick ons and go get the real McCoy.
Hey man, I use what I gots! My machines are nice and level, my toilet seat, well... Had to get the parts from somewhere.
Anyway, being that it's a BP we are talking about, really don't matter at all. Column, and therefor accuracy, will be uneffected either way, don't really matter how you support the base, toilet seat bumpers, hockey pucks, or directly on 12" of reinforced concrete.
I've never been a big fan of those supposedly "vibration dampening" leveling feet. In my experience, they usually have the opposite effect. I seem to be joined in this mind set by all the machine tool makers that I am aware of, all their publications recommend their machines being installed solidly on a floor and leveled with either shims(in specific locations), or jack screws provided in the machine base. Never read anywhere to put some chunks of rubber in there.
Only thing the rubber feet are any good at in my book is vibration ISOLATING, which is a much different animal and vibration dampening. If you have a machine that creates a lot of vibration, by all means, use rubber pads to isolate it from the floor so the vibration is not transmitted through the shop.
I always get a kick out the guys who have the rubber feet under a lathe, or other flimsy bed machine, and are trying to level it. Just not gonna happen!